1. Field of the Invention
The present invention relates generally to power supplies, and more particularly, to a power supply having an auxiliary power cell.
2. Related Art
Electrochemical power cells, solar power cells, fuel power cells, etc, (generally and collectively referred to as “power cells” herein) are used to generate and/or store electrical energy. One or more power cells are conventionally used to power a wide range of devices, equipment and structures. For example, it is well known to use a power supply having one or more power cells to power personal electronics such as portable audio players, cell phones, computers and the like, equipment such as cars or other machinery, and even structures, such as homes, offices, etc, (generally and collectively referred to as “powered systems” herein). Powered systems generally require the power supply to provide a threshold quantity of power to the system load (e.g. functional components) so that the powered system may operate effectively and consistently. For example, if a power supply provides insufficient power, a powered system may fail unexpectedly or erratically.
The ability of a power cell to output power, sometimes referred to as the power cells' power delivery capability, may be limited by the power cell's size, shape, type, condition, etc. As such, a plurality of power cells is typically electrically connected in series to supply sufficient power to the powered system. A particular problem associated with conventional power supplies is that failure of a single power cell may limit the power available to the powered system, thereby causing performance of the system to degrade, or causing unexpected system shutdown. For example, a decrease in the operating voltage of a single power cell could result in total system shutdown or failure. As used herein, the operating voltage of a power cell (sometimes simply “voltage” herein) refers to the voltage across the terminals of the power cell while the power cell is supplying power to a load.
In certain powered systems, loss or interruption of power results in, for example, total system failure, loss of information, or damage to the various components of the powered system. As such, unexpected or erratic failures, or failure to meet additional power demands, is undesirable, and, at times, unacceptable. Examples of powered systems in which such failures are often unacceptable include medical prostheses such as neural stimulators, pacers, drug pumps, hearing prostheses, and the like.
To avoid unexpected or erratic failure, certain powered systems alter or control the power consumption of the system when insufficient power is provided by the power cells. For example, certain powered systems successively implement a series of operational states each requiring less power than its immediate preceding state. Each state uses the remaining available power so that damage to the system or loss of information is reduced or eliminated prior to total system shut down. The power system may continue to operate in one of these states using the available power to operate only critical components, or the system may eventually shut down. Although damage to the powered system may be avoided, the ability to extend meaningful operation of the system beyond interruption of power is not possible.